Temperature-regulating means for filamentary electrodes



'A. L. ATHERTON.

TEMPERATURE REGULATING MEANS FOB FILAMENTARY ELECTRODES.

APfLlc/Tlon FILED :1111.29.1911. 1,406,328, Patented Feb. 14, 1922.v

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AT'ToRNEY PATENT OFFICE.

UNITED STATES ALFRED L. ATHERTON. OF EDGEWOOD PARK, PENNSYLVANIA,ASSIGNOR T0 WEST- INGHOUSE ELECTRIC AND MANUFACTURING COMPANY, ACORPORATION OF PENN- SYLVANIA.

TEMPERATURE-REGULATING MEANS FOR FILAMENTARY ELECTRODB.

Specication of Letters Patent. Patented Feb. 14, 1922,

Application led January 29, 1917. Serial No. 145,239.

To aZZ lwhom it may con cem.:

Be it known that I. ALFRED L. ATHERTON, a citizen of the United States,and a resident of Edgewood Park, in the county of Allegheny and State ofPennsylvania, have invented a. new and useful Improvement inTemperaturerRegulating Means Ifor Filamentary Electrodes, of which thefollowing is a specication.

My invention relates to heat-regulating means for tlamentary electrodes,such, for example, as the cathodes of hot-cathode convertel-s, and ithas for its object to provide apparatus of the character designatedwhereby an electrode may be maintained at substantially a predeterminedtemperature, irrespective of changes in the load current flowingthereto.

In the accompanying drawings, Fig. 1 is a diagrammatic view of aconverter of the hot-cathode type, together with auxiliary heating andload circuits, embodying a preferred form of my invention; and Figs. 2to 6, inclusive` are diagrammatic views of inodifications of the systemshown in Fig. 1.

It is well known that, if two electrodes be placed in proximity toeachother, one electrode being sufficiently hot to emitpelectrons and theother being comparatively cold, and an alternating electromotive forcebe impressed across said electrodes, current waves will flow to the hotelectrode as a cathode and will not flow in the reverse direction.

T he above-noted principle has been quite widely employed in convertersAfor changing alternating currents into direct currents and also forwireless detectors and other analogous uses.

In the various embodiments of this principle, the two electrodes aregenerally placed within a closed container and said container is eitherhighly evacuated or is 'charged with an inert gas, such, for example,ias argon or nitrogen. The cold electrode is generally given the form ofa mass of refractory material, such, for example, as tungsten or carbon,and the hot electrode is generally formed, in a filamentary shape, froma similar refractory material. The -cathode is maintained ata suitabletemperature for starting and operating the device by passing heatingcurrent thereto from an auxiliary current source. i

It is obvious that, with apparatus of the character designated, ifsufficient heating current from the auxiliary source is initially passedthrough the ilanientary electrode to start the device into operation,the subsequent iiow of load current will still further heat saidflamentary electrode, leading to the danger of overheating the same. Itis, therefore, desirable that the amount of auxiliary heating current bedecreased with an increase in the load current so that the filament maybe maintained at all times at a substantially uniform temperature, saidtemperature being suiiiciently high to maintain a pronounced electronicemission but not so high as to cause the ilamentary electrode to beunduly short-lived.

Apparatus to fulfil the above conditions may be developed in a greatvariety of different forms, as will hereinafter more fully appeal'. i

Referring to Fig. 1, a converter is shown at 7 said converter comprisinga closed container 8 provided with an anode 9 and with a filamentarycathode 10. Energy for the operation of the converter 7 is supplied fromany suitable source, such, for example, as a transformer 11 embodying aprimary winding 12, a main secondary winding 13 and an auxiliarysecondary winding 14. The three windings 12, 13 and 14 are mounted on acommon core 15, the main secondary winding 13 beingin relative-ly closeproximity to the primary winding 12, whereas the auxiliary secondarywinding 14 is quite widely removed from said primary winding. The twotreminals of the main secondary winding 13 are connected, respectively,to the anode 9 and to the cathode 1 0 through asuitable load device 16.The two terminals of the auxiliary secondary winding 13 are connected,respectively, to the two terminals of the tilamentary cathode 10.

The operation of the apparatus thus described is as follows. Uponsupplyin energy to the primary winding 12, an e ectromotive' force isdeveloped in the auxiliary secondary winding 14 which causes current t0flow through the ilamentary cathode 10, raising the latter to anelectron-emitting temperature. When this condition is reached, alternatehalf waves from the main secondary winding 13 flow from the anode 9 tothe cathode 10 and back through the load, establishing the load currentof the device.

VThe load current would tend to still further heat the cathode were itnot for the fol- A tween the primary winding 12 and the secondarywinding 13. The leakage flux is subtracted from the flux formerlytraversing the auxiliary secondary winding 14, and the electromotiveforce produced in said auxiliary secondary winding is, therefore,decreased, reducingl the iiow of auxiliary heating current to thefilament. 10.

With a decrease in the load current, the converse action takes place.The reduction in the magnetomotive force of the secondary winding 13permits an increase in the fiux traversing the auxiliary secondarywinding 14 and, therefore, increases the heating current supplied to thecathode 10.

Referring to Fig. `2 for a modified form of my invention, I show aconverter 7, as before, deriving its energy from a transformer 11provided with windings as described except that the two secondarywindings may have an equally close relation to the primary winding. Thefilamentary cathode 10 may be energized from the secondary winding 14 bylosing a suitable switch 17 in its upper position.

An auxiliary transformer 18, similar to the ordinary constant-currenttransformer, is also'provided for the energization of the lamentarycathode 10. Said transformer comprises a fixed primary winding 19 whichis inserted in the vload circuit of the device and a movable secondarymember 20 which is counter-weighted, as indicated. The counter-weightingsystem is such that the device has an inverse ratio, that is to say., aninc rease in the primary current causes such repulsion of the secondarywinding as to actually decrease the secondary circuit, as distinguishedfrom the ordinary constant-cnrrent transformer wherein the secondarycurrent remains substantially constant over l wide changes in theprimary current.

Having initiated operation in the apparatus of Fig. 2 by the closure ofthe switch 17 in its upper position, said switch is thrown to its lowerosition, whereupon the filament 10 is trans erred from the secondarywinding 14 of the main transformer to the secondary winding 20 of theauxiliary transformer and thereafter, so long as the apparatus remainsin operation, the effect of the auxiliary transformer 18 is to maintainsubstantially uniform heat in the filament 10, irrespective of changesin the load current. Referring to the form of my invention shown in Fig.3, the main parts of the system are as before, and an auxiliary currenttransformer 21 is provided in addition. The primary windingof saidauxiliary transformer is connected in the load circuit and the secondarywinding thereof is connected in the auxiliary heating circuit so thatits electromotive force opposes that of the secondary winding 14. Underthese conditions, the effect of the'transformer 21 is negligible untilthe flow of load current is initiated, whereupon an electromotive forceis produced in the secondary winding thereof which is proportional tothe load currentV and, therefore, tends to neutralize the electromotiveforce of the winding 14 and to reduce the heating current with anincrease in the load current.

In the form of my invention shown in F ig. 4, the filamentary cathode isshown deriving its heating current from an auxiliary source -of directcurrent 22, as is frequently the case. Said auxiliary heating currenttraverses an adjustable resistor 23 which is under the control of asolenoid 24 or other electromotor device. The arrangement is such that,when no load current is flowing, the effective value of the resistor 23is a minimum, permitting the fiow of a maximum heating current. As theload current increases, more and more of the resistor 23 is inserted incircuit, and the heating current derived from the battery 22f is reducedin amount, resulting in the desi-red maintenance of substantiallyuniform temperature at the cathode 10. If an alternating source beemployed for the heating current, such, for example, as an auxiliarysecondary Winding on the supply transformer, the load` responsiveregulating device would preferably take the form of an adjustablereactor rather than the form of an adjustable resistor.

Thermostatic means may be employed, if necessary in order to achieve thedesired end. A system of this type is shown in Fig. 5 wherein athermostatic device 26 is mounted in proximity to the container 8 of aconverter 7, said thermostat being preferably mounted adjacent to thecathode 10. A'heating coil 27 surrounds the thermostat 26 and isinserted in a portion of the circuit carrying only load current. Acontact member 28 is so mounted that the thermostatic member 26 makescontact therewith when cold. A resistor 29 is normally connected in thecircuit of the circuit of the auxiliary heating current so -as to be inseries with the cathode 10. In operation, at starting, the thermostaticmember 26 is cold and rests against the contact member 28, shortcircuiting the resistor 29 and permitting the fiow of a large heatingcurrent tothe cathode 10. When the thermostat 26 is heated by the jointaction of the cathode 10 and of the heating coil 27, contact is brokenwith the member 28, and the heating current is forced to traverse theresistor 29, thus being radically diminished in amount. Obviously, thethermostat 26 may be caused to depend entirely upon either the container8 or upon the heating coil 27 as a heating source.

In the form of my invention shown in Fig. 6, a resistor 30 is includedin the load circuit and mounted in close proximity to a resistor 31mounted in the auxiliary heating circuit. The resistor 30 is soproportioned that it varies in temperature with changes in the loadcurrent. The resistor 31 is a conductor of the first class and is soproportioned that it is not heated to any great extent by the flow ofheating current therethrough. Thus, at the start, the auxiliary heatingcurrent vtraverses the resistor 31 with but little op osition because ofthe resistance thereof. ith the initiation of load current, the resistor30 becomes hot and transmits heat to the resistor 31 in such amount asto radically increase the resistance thereof, thus cutting down theamount of auxiliary heating current.

It is obvious that my invention `is susceptible of still further changesand alterations without departing from the spirit thereof Y and elementsshown in certain figures might equally well be em loyed in systems ofcertain other of the gures. Furthermore, it is obvious, for example,that, instead of introducing the 4resistor 29 in series with thefilament 10 in the system of Fig. 5, the thermostat 26 might be employedto close a shunt path around said filament, but changes of thischaracter come within the province of the skilled electrician and do notcause systems embodying the same to -be patentably distinct from eachother.

While I have shown my invention in a plurality of forms, it is not solimited but is susceptible of various minor changes and modificationsWithout departing from the spirit thereof and I desire, therefore, thatonly such limitations shall be placed thereupon as are imposed by theprior art or asare indicated in the appended claims.

I claim as my invention: y

1. The method of operating a filamentary space-current device,consisting in causing a heating current and a load current to passthrough the filament and causin the heating current to decrease when theoad current increases, and vice versa, in such manner as to maintain thefilament temperature substantially constant.

2. The combination with an electric apparatus embodying a closed tubeprovided with an anode and a filamentary cathode, of

means for assing a heating current through said catho e, means forpassing a load current between said electrodes, and control means forautomatically decreasing said heating current in response to an increasein said load current, whereby said filamentary cathode is maintained atsubstantially a uniform temperature.

3. The combination with an electric apparatus embodying a closed tubeprovided with an .anode Vand a filamentary cathode, of means for assinga heating current through said catho e, means for passing a load currentbetween said electrodes, and a currentresponsive device subject to theaction of the load current and operative to inversely adjust the amountof said heating current.

4. The combination with an electric apparatus embodying a closed tubeprovided with an anode and a iilamentary cathode, of means for assing aheating current through said catho e, means for passing a load currentbetween said electrodes, and a currentresponsive device subject to theaction of the load current and operative to decrease said heatingcurrent with an increase in said load current and vice versa.

5. The combination with an electric apparatus embodyin a filamentaryelectrode, of means for feedln both a load current and an auxiliaryheating current to said filament and automatic means for adjusting saidheating current in an inverse relation with respect to said loadcurrent.

6. The combination with an electric apparatus embodying a closed tubeprovided with an anode and a filamentary cathode, of means for passing aheating current through said cathode, means for passing a load currentbetween said electrodes, said filamentary cathode being heated both bysaid heating current and by said load current, and means controlled bysaid load current and automatically operative to regulate said heatingcurrent so as to maintain said filamentary cathodeat a constanttemperature.

7. The method of operating a lamentary rectifier consistino in passing aheating current and a loadJ current through the filament andmagnetically controlling the relative amounts of said currents to effectan increase in one as the other decreases and vice versa.

In testimony whereof, I have ,hereunto subscribed my name this 20th dayof J anuary 1917.

ALFRED L. ATHERTON.

